solderdude
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Post by solderdude on Sept 3, 2013 20:25:42 GMT
I've uploaded a complete "shopping list" for the page 35 version of the T50RP filter to Google docs. You can find it here: docs.google.com/file/d/0B_svLQu7hxPtQlJHUzdJTFU5UEk/edit?usp=sharingSome specific questions: Because I'm using the recommended DCDC converter, do I need to change anything re: rectifiers? Any particular recommendations for wire? a short answer as I am off to bed early today. just use the recommended components for option 4. Preferably the 5V power supply wires should not be connected to the ground/enclosure. No need to change anything on the power supply side. wire... just use plain wire, as long as everything remains inside a shielded enclosure you do not need screened wiring. Also no need to use thick wiring. DO keep the power supply wires a bit away from the audiolines if possible. IF wires cross closely to the power wires try to do so under 90 degrees angle. might have a look at the component list tomorrow but the next few days my time is very limited. |
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Post by micmacmo on Sept 3, 2013 22:30:28 GMT
Thanks, Frans. Any suggestions welcome. BTW, all parts are currently available from Digikey in North America. (I chose to go with one vendor to avoid the crazy shipping and brokerage fees we face in Canada when getting shipments from the US.)
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solderdude
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Post by solderdude on Sept 4, 2013 6:40:06 GMT
List looks good.
Personally I feel 1% tolerance is not needed and increases the price.
The E12 series will do just fine but using 1% won't hurt for sure (except the wallet)
My experiences with the selected RCA sockets is that when you tighten them firmly the thread breaks.
That was over 10 years ago though, maybe a different manufacturer or improved quality is now available.
Perhaps buy 2 spares just to be safe, they are cheap.
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Post by micmacmo on Sept 5, 2013 3:57:00 GMT
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solderdude
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Post by solderdude on Sept 5, 2013 6:41:10 GMT
www.digikey.ca/product-detail/en/1622389-1/A105956CT-ND/3477533 look fine. SFR16 is small sized. You could fit SFR25 sizes (the 'standard' size) but the bend would be really tight. Carbon film can be used but for Rx02, Rx11, Rx14 I would choose metal film. of course all metal film is good as well. Power ratings are not important in this case as powers involved are very small.
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Post by micmacmo on Sept 6, 2013 5:13:16 GMT
Frans, I think you're the first person who's ever recommended I spend less money on this hobby. Thanks! I've uploaded a revised shopping list for the page 35 version of the filter to Google docs. You'll find it here: docs.google.com/file/d/0B_svLQu7hxPtcEh3T21NSmNWMVU/edit?usp=sharingThe purpose of this "shopping list" and an explanation of what's included is discussed in my post above: diyah.boards.net/post/3516/thread I'm hoping this one will be golden and I can start ordering parts! (I'll do a similar list for the AKG k701 filter too.) |
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solderdude
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Post by solderdude on Sept 6, 2013 6:51:32 GMT
Looks O.K. (checked only a few parts though)
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Deleted
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Post by Deleted on Sept 8, 2013 20:58:10 GMT
guess which muppet bought wire too big to to pass through the holes on the filter board?  hoping to finally finish it tomorrow now |
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Post by micmacmo on Sept 9, 2013 0:44:49 GMT
I feel your pain. (Care to share what gauge of wire didn't fit?)
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solderdude
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Post by solderdude on Sept 9, 2013 6:39:17 GMT
For all internal wiring I use unscreened thin and supple multicore instrumentation wiring.
The holes can accomodate 0.9mm diameter wires (holes are slightly smaller than 1mm)
specs:
Conductor Area CSA: 0.22mm²
Jacket Colour: Red
Jacket Material: PVC (Polyvinyl Chloride)
Conductor Material: Copper
External Diameter: 1.2mm
Voltage Rating: 1kV
No. of Max Strands x Strand Size: 7 x 0.2mm
SVHC: No SVHC (19-Dec-2012)
Current Rating: 1.4A
Primary Insulation Thickness: 0.3mm
Standard: DEF61-12(Part 6) Type 2, BS4808 Part 2
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Post by Deleted on Sept 9, 2013 17:43:07 GMT
Frans
thanks for the info on the cable size.
i finished wiring the filter board today but unfortunately there is no sign of life from it.
the first issue was down to me. if you remember i said my power socket was grounded to the case. well i forgot all about that and connected it anyway.
i did check that polarity was ok though. went to maplin to try and get an isolated socket, but they do not stock the type i wanted, only the ugly looking surface mount version.
i returned home and removed the fitted socket from the case, and connected it externally just to see if there was any difference, but no change.
i then thought to double check my wiring, using continuity . wiring appears ok. but i did notice the +v and -v have virtually a dead short across them. (around 25 ohms).
surely this cant be right?
any ideas?
i am sure i have done something wrong
cheers
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Post by Deleted on Sept 9, 2013 18:09:02 GMT
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solderdude
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Post by solderdude on Sept 9, 2013 18:51:49 GMT
It is possible the DCDC converter has a reverse diode that you may be measuring.
In that case all is O.K.
Even when you used a grounded powersocket it is no problem.
At least as far as I know you have a DCDC converter on the PCB (i.e. power option 4)
In this case even a grounded socket won't destroy any components.
these e-bay sockets look nice.
some sockets have 3 pins where one of them is a switch which opens when a plug is inserted (so a battery might be disconnected if applicable)
If connected wrongly you may either not get any voltage at the pins or you can 'see' a short with a multimeter but this disappears when a plug is inserted.
I recommend to put the PS in the socket (when still unconnected) and measure the voltage on the socket pins to ensure you got the +/- correct.
In power option 4 only reverse polarity or over voltage can kill the DCDC converter.
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Post by Deleted on Sept 9, 2013 19:17:16 GMT
It is possible the DCDC converter has a reverse diode that you may be measuring. In that case all is O.K. Even when you used a grounded powersocket it is no problem. At least as far as I know you have a DCDC converter on the PCB (i.e. power option 4) In this case even a grounded socket won't destroy any components. these e-bay sockets look nice. some sockets have 3 pins where one of them is a switch which opens when a plug is inserted (so a battery might be disconnected if applicable) If connected wrongly you may either not get any voltage at the pins or you can 'see' a short with a multimeter but this disappears when a plug is inserted. I recommend to put the PS in the socket (when still unconnected) and measure the voltage on the socket pins to ensure you got the +/- correct. In power option 4 only reverse polarity or over voltage can kill the DCDC converter. Hi Frans i am actually option 3, if that helps your diagnosis? i do indeed have the 3 pin socket, i think i may have attached the neg to the wrong pin. pos is definitely connected to centre pin though. will try again in the morning. thanks mate |
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solderdude
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Post by solderdude on Sept 9, 2013 19:32:20 GMT
Ah right... for option 3 it MUST be isolated from ground other wise the opamps have died and gone to audio heaven.
There could have been +24V on a pin that can handle max 15V when power was applied.
Still you could measure the input of the circuit in the diode setting and do 2 measurements.
One with the red lead on + and black lead on - and one reading with the red lead on - and black lead on +
If they read the same in those 2 conditions something is fishy.
What you can do is remove the socket from the enclosure.
connect a few wires and leave it outside of the enclosure.
remove the 4 opamps
Measure the DC voltages with respect to ground.
There should be +/-12V (or very close to it).
It is always a good thing to test the power supply voltages before inserting the op-amps in the build of this amp.
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